The proper design of electrical connectors plays an increasingly important role in the design of electrical circuit wiring. This is especially true in aircraft technologies, because of the requirements imposed by strict safety and reliability standards. Military aircraft present even greater requirements in this regard, in part due to the severe physical stresses that may be experienced by avionics systems. An overall requirement that aircraft weight be minimized presents particular problems for electrical circuit wiring design.
In modern military aircraft, the wiring which is provided for low-current signal communications may constitute as much as 40% of the total length of the wiring on board the aircraft. This percentage continues to increase and is made possible by the development of stronger wires having improved insulation. There is therefore a need to use smaller wire sizes which provide for significant weight reduction. The difference in weight between two wires which are three wire sizes apart may be as much as 50%, such that use of smaller signal wire having wire sizes 24 or 26 is desirable to provide a substantial weight savings over use of larger wire having wire size 22, for example.
However, the smaller signal wire presents difficulties for existing electrical connectors, notably pin connectors. These connectors are of a type wherein an integral wire barrel is designed with an inside diameter appropriate for the wire size being used. An exposed end of the insulated wire is inserted into the wire barrel where it is crimped to provide electrical and mechanical connection to the pin connector. Because of the rigidity of the connection, there is a weak point created in the wire just beyond the wire barrel where exposed wire is sometimes visible. This weak point has presented the very serious problem of breakage, resulting in the increase of electrical failures.
In some designs, the pin connector is encapsulated in an insulation gasket or seal to provide additional strength to the connection. Nevertheless, very often the problem of wire breakage or wire pullout is observed when smaller wire sizes are used due to the existence of the weak point as described above. One solution that has been considered is the use of larger wire sizes, but for existing applications this involves extensive and costly rewiring.
An illustration of the severity of the problem can be recognized in the report that existing military specifications for F-15 and F-16 fighter aircraft were recently revised. Whereas pin connectors using smaller wire having wire sizes 24 and 26 were permitted under MILSPEC W5088 Issue J, such pin connectors were eliminated in favor of pin connectors using larger wire having wire size 22 under Issue K. This revision is unfavorable because of the additional weight resulting from the use of the larger wire size, which may amount to as much as 50 kilograms on the aircraft. There is also the significant aspect of rewiring costs involved. These problems have also been encountered in the design of new fighter aircraft such as the Lavi fighter currently being developed by Israel Aircraft Industries.
It would therefore be desirable to eliminate the weak point in wiring terminations made by various types of connectors such as pin connectors which are used for wire terminations of smaller wire sizes.